Fuel supply system

ABSTRACT

In a fuel supply system for an externally ignited internal combustion engine with compression of the fuel/air mixture, in which air flow-measuring means and a randomly operable throttle valve are arranged successively in the air intake suction pipe of the engine, and the meauring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces the movable member of a distributing valve arranged in the fuel line in order to meter a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pressure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, there is described an improved control cell adapted for temperature-dependent operation and which comprises a cell housing, bimetallic spring means, and heat-conducting tongue means jointly mounted in the housing for the conduction of heat from the tongue means to the bimetallic spring means and insulated against heat losses to the housing, electrical heating means associated with the tongue means, and fuel pressure regulating means comprising a control spring mounted in the housing, the bimetallic spring means being adapted for engaging the control spring and reducing the force of the spring at temperatures below the operational temperature of the engine.

United States Patent [191 Knapp 1 FUEL SUPPLY SYSTEM [75] Inventor:Heinrich Knapp,

Leonberg-Silberberg, Germany 1 s g w R999! B9 91 mbH St Germany 22Filed: Aug. 9, 1973 21 Appl. 190.; 386,980

[30] Foreign Application Priority Data Sept. 7, 1972 Germany 2243921[52] US. Cl... 123/119 R, 123/139 AW, 123/179 G [51] Int. Cl F02m 69/00[58] Field of Search..... 123/119 R, 139 AW, 179 G PrimaryExaminer-Manuel A. Antonakas Assistant ExaminerS. J. Richter Attorney,Agent, or FirmEdwin E. Greigg [5 7] ABSTRACT In a fuel supply system foran externally ignited internal combustion engine with compression of thefuel- 1 Sept. 17, 1974 lair mixture, in which air flow-measuring meansand a randomly operable throttle valve are arranged succes sively in theair intake suction pipe of the engine, and the meauring means is moved,in proportion to the air amount flowing through the suction pipe,against an at least substantially constant resetting force and therebydisplaces the movable member of a distributing valve arranged in thefuel line in order to meter a fuel amount proportional to the airamount, and wherein a pressure liquid of at least substantially constantpressure, which is continuously delivered through a pres sure line,serves to transmit the resetting force and acts upon a control slidevalve to effect the resetting, the pressure of the liquid being variableby means of at least one regulated pressure control valve which iscontrolled in dependence on characteristic engine data, there isdescribed an improved control cell adapted for temperature-dependentoperation and which comprises a cell housing, bimetallic spring means,and heat-conducting tongue means jointly mounted in the housing for theconduction of heat from the tongue means to the bimetallic spring meansand insulated against heat losses to the housing, electrical heatingmeans associated with the tongue means, and fuel pressure regulatingmeans comprising a control spring mounted in the housing, the bimetallicspring means being adapted for engaging the control spring and reducingthe force of the spring at temperatures below the operationaltemperature of the engine.

4 Claims, 2 Drawing Figures v v v v v v vv v v w v vv PATENIEU SEH 1:914

SHEET 1 OF 2 j////// ////I///// III PAIENImSEP 1 71914 SHEEI 2 OF 2 hagn E:

FUEL SUPPLY SYSTEM BACKGROUND THE INVENTION valve are arrangedsuccessively in the air intake suction pipe of the engine, and themeasuring means is moved, in proportion to the air amount flowingthrough the suction pipe, against an at least substantially constantresetting force and thereby displaces the movable member of adistributing valve arranged in the fuel line in order tometer a fuelamount proportional to the air amount, and wherein a pressure liquid ofat least substantially constant pressure, which is continuouslydelivered through a pressure line, serves to transmit the resettingforce and acts upon a control slide valve to effect the resetting, thepressure of the liquid being variable by means of at least one regulatedpressure control valve which is controlled in dependence oncharacteristic engine data, and which contains a control cell whoseoperation is temperature-dependent.

It is a problem of known fuel metering systems of the above-describedtype that the heating-up period of the internal combustion engine is ofdifferent length depending upon the starting temperature, and that thetemperature rise is much steeper in a heating-up period beginning at astarting temperature of +C than in such period beginning at a startingtemperature of 20C. To obtain an ideal enrichment of the fuel mixtureduring the heating-up period, a control cell whose operation istemperature-dependent would be required in the pressure control valve,which in turn would effect the control pressure of the fuel meteringsystem with the same time/temperature dependency as it would affect theheating-up of the engine.

It has been proposed to solve this problem by means of a systemcomprising an element of heat-expanding material or a heated bimetalspring, either of which achieves control of the fuel enrichment duringthe heating-up phase. However, such elements can not bring about anexact adaptation of the rise in control pressure to the actual,momentary rise of the engine temperature. Such elements could onlyachieve an exponential rise of the control pressure.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the presentinvention to provide improved control cell means in the pressure controlvalve of a fuel supply system in an engine of the type describedhereinbefore, which cell means can vary the control pressure of apressure liquid serving as a resetting force on an air flow measuringdevice, in a better approximation to the temperature rise during theheating-up period of the above-described type of engine, than do thehitherto known means.

This object is attained according to the invention by providing, as thecontrol cell means in a fuel supply system of the type described above,a bimetal spring which is coupled to a heat-conducting tongue or stripheated immediately after starting by an electrical heater element. Themounting of the bimetal spring is heatinsulated against the surroundingparts of the system, and, at temperatures below the operationaltemperature of the engine, the bimetal spring acts against the force ofa control spring of the pressure control valve mentioned hereinbefore.This arrangement has the advantage that, while the curve of thetemperature rise with time is still exponential, its curvatures are sostretched due to delay in heating-up the bimetal spring that there isobtained with good approximation a substantially linear characteristicwhich accords well with the linear characteristic of engine heat-up.

According to another embodiment of the invention, the heat-conductingtongue consists of a metal strip disposed in parallel with the bimetalspring and being in heat-conductive contact with the bimetal spring attheir joint fastening point. On the free tongue end there is mounted anelectrical heater element, and the metal strip may bend to adopt varyingdistances from the bimetal spring, in accordance with a controllablevarying heat transfer by radiation onto the bimetal spring. As anadvantage hereof, the heating of the bimetal spring can be regulatedaccording to the requirements of the engine run with fuel from the fuelsupply system improved according to the invention.

In a further advantageous embodiment of the invention, an electricalseries resistance can be switched into the current lead-in of theelectrical heater element, at low starting temperatures, by means of asecond bimetallic spring. This affords an even slower heating-up of thebimetal springs in accordance with the actual conditions prevailing inthe engine at low starting temperatures, and, thereby, the controlpressure is adjusted in accordance with the flat-shaped engine heat-upcurves corresponding to low starting temperatures.

The invention will be better understood and further objects andadvantages will become apparent from the ensuing detailed specificationof preferred but merely exemplary embodiments taken in conjunction withthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematical view of a fuelsupply system containing a preferred embodiment of control cell meansaccording to the invention, and

FIG. 2 shows a diagram in which the temperatures and the controlpressures of the pressure liquid, shown on the ordinate, are plottedagainst the time, shown on the abscissa, with temperature-time curvesfor the heatup of the engine being interposed therebetween.

DESCRIPTION AND OPERATION OF THE PREFERRED EMBODIMENT In FIG. 1 there isshown a fuel supply system in which air for combustion flows in thedirection indicated by arrows through an air filter 1 into a zone 3 ofan airintake suction pipe, in which zone a measuring plate 4 isarranged, and further, through a flexible connecting tube 5, into a zone6 of the suction tube, which zone 6 contains a randomly operablethrottle valve 7; from suction tube zone 6, the air flows into one orseveral cylinders (not shown) of the internal combustion engine. Themeasuring plate 4 is disposed in zone 3 transversely to the direction ofair flow, and is displaceable in that zone in accordance with anapproximately linear function of the air amount flowing through thesuction tube. In this arrangement, the pressure prevailing between themeasuring plate 4 and the throttle valve 7 remains constant, as long asthe resetting force acting on measuring plate 4 and the air pressureprevailing upstream of measuring plate 4 also remain constant. Meaawayfrom nose ll.

lulu, uunsuring plate 4 controls directly a fuel metering anddistributing valve 8. The displacements of measuring plate 4 aretransmitted by means of a lever connected thereto and being adapted forswivelling motion about a pivot 9, and from lever 10 via a protrudingnose [1 to a control slide 12 hearing nose l1 and being displaceable inaxial direction in a central bore 22 of central housing 8b of the fuelmetering valve 8.

Central valve housing 8b is surrounded by an external housing part 80.Fuel serving as a pressure liquid acts as a resetting force formeasuring plate 4 on the frontal face 13 of control slide 12 at theopposite end of the latter from nose 11.

The supply of fuel to fuel metering valve 8 takes place by means of afuel pump 16 driven by an electromotor 17. Pump 16 aspirates fuel from afuel reservoir 36 and delivers it via a fuel line 18 into a duct 19provided in the external annular housing part 8a of fuel metering valve8. Duct 19 opens into an annular groove 20 extending about the peripheryof central housing 812 between the latter and external housing part 812.Radial bores 21 lead from annular groove 20 to the central bore 22 ofcentral housing 8b. Central axial bore 22 houses the control slide 22which latter is of cylindrical shape and has in its middle portion acircumferential groove 23 constituted by a reduced diameter portion ofslide 12 between the two full diameter end portions thereof.

Depending upon the position of the control slide 12 in axial bore 22,slide groove 23 will register more or less completely with radialcontrol slots 24 and 24 extending from the inner wall of bore 22 throughcentral valve housing 8!) and communicating with ducts 25 and 25',respectively, which are provided in the external housing part 8a and areconnected to fuel-injection valves (not slgwn) of the internalcombustion engine, thus permitting metered fuel to flow to theseinjection valves. A part of the fuel from annular groove 20 flows via abypass duct 26 into an annular groove 27 provided in the periphery ofcentral housing 8b and external housing part 8a in the end portion ofcentral housing 8a away from slide nose 11. Annular groove 27communicates with a fuel line 29, leading away from the housing of valve8, via radial bores 28. On the other hand, groove 27 communicates viathe same bores 28 and via a throttle passage 30 with a pressure chamber31 being defined in central bore 22 between the end wall of the latterand the frontal face of control slide 12 Fuel flowing via line 29 to apressure control valve 32 serves as the pressure fluid in the controlsystem now to be described. Valve 32 is a flat seat valve comprising amembrane 33 and rigid valve seat constituted by the rim of lead-in duct34 into which line 29 opens. Overflowing excess fuel is recycled freefrom pressure through a return line 35 back to fuel reservoir 36. Valvemembrane 33 is biassed by means of a spring 37 whose initial tension isvariable in dependence on engine data. This is achieved by means of acam 38 which is mounted on a shaft 39, bearing the flap of throttlevalve 7, for rotation with the latter, and is axially displaceable alongshaft 39 in dependence on the reduced pressure prevailing in the suctiontube downstream of throttle valve 7. A rotation of shaft 39 istransmitted to cam 38 by means of an angle-shaped key 40. The free endof cam 38 is rotatably mounted in a bearing 41a fastened on the adjacentface of a membrane 41 which separates the interior of valve 32, housingcam 38, from a reduced-pressure chamber 42. The latter is connected bymeans of a line 43 to the zone 6 of the suction tube downstream ofthrottle valve 7. if there is a sufficient reduction of pressure inchamber 42, cam 38 will be moved axially against the force of acompressible resetting spring 44. A pencil-shaped pin 45, the blunt endof which follows cam 38, will be axially displaced by the movement ofcam 38 and abuts with its opposite end the inner wall of aspring-retaining cap member 46. Displacement of the latter caused by theaxial displacement of pin 45 will compress spring 37 which is retainedby cap member 46. The degree of compression of spring 37 determines thepressure exerted by pressure liquid to reset the measuring plate 4.

A fuel line 50 branches off from line 29 and conveys fuel to a secondpressure control valve 53 through fuel inlet 54, and fuel is recycledfrom valve 53 to the fuel reservoir36 through a fuel return line 55.Pressure control valve 53 affords a temperature-dependent regulation ofthe resetting pressure exerted by the fuel portion serving as pressureliquid; this valve 53 comprises ing of fua inlet tube 57 which openingisobttirated by a valve membrane 58 which is biassed by a membranespring 59 in valve-closing direction. A tubular connecting member 60 isfastened at its one end in a bearing 61 attached to membrane 58 andrests with its other end in a bearing 62 attached to membrane spring 59,thus transmitting the valve-closing force of the latter spring to theformer membrane. A bimetallic blade spring 64 is fastened at its one endby means of a nut 67 to a bolt 65 mounted in the housing 53a of valve53, while the other, free end of bimetallic spring 64 protrudes into theinterior of valve housing 53a and is provided with a forked end 64aadapted for engaging bearing 62 on membrane spring 59. An insulatingmeans 66 is placed between bolt 65 and bimetallic spring 64 and preventsheat losses by the spring due to heat conduction to the housing 530 ofvalve 53. A heat-conducting tongue 68 is fixed on bolt 65 jointly withbimetallic spring 64. it extends substantially parallel to thebimetallic spring 64 in valve housing 53a and is in heatconductingcontact with spring 64 through their common mounting on bolt 65.

An electric heating coil 69 is mounted on tongue 68 and is connected tothe plus pole of a current source through lead 70 and to ground via alead 72 having a branch point 71 from where a first branch leads toanother bimetallic spring 73 mounted in the wall of valve housing 53a toinsure an adequate electrical insulation, the tongue of which bimetallicspring is adapted for making contact with contactor 76 connected toground, and from where a second branch leads to contactor 76 via aseries resistance 74 which can be bridged by bimetallic tongue 75.

Spring membrane 59 can also be replaced by another type of spring havinga non-linear characteristic or a helical spring, in which case thetension could be varied by an adjusting screw mounted in the valvehousing 53a and acting on a spring retaining disk or the like means,thus offering further possibilities for adjustment.

The fuel supply system provided with the control cell means according tothe invention operates in the following manner.

gilat valve seat constituted by the rimabout the open:

When the internal combustion engine is running, pump 16 driven byelectromotor 17 aspirates fuel out of fuel reservoir 36 and delivers itunder pressure via line 18 to metering valve 8. Simultaneously, theinternal combustion engine aspirates air into the suction tube (3, 5, 6)and the air flow displaces the measuring plate 4 from its rest positionshown in FIG. 1.

In accordance with the displacement of measuring plate 4, lever which isrigidly attached to measuring plate 4 moves control slide 12 into axialbore 22 whereby communication between slots 24, 24 and annular groove 23is widened and a greater cross sectional area is formed for the passageof fuel passing through slots 24, 24'. The increased fuel amount thusflowing through passages 25 and 25' to the injection valves (not shown)corresponds to the distance by which measuring plate 4 has moved fromits rest position. Part of the fuel passing through annular slide groove23 flows through duct 26 into pressure chamber 31, thus exertingpressure on the frontal face 13 of control slide 12, and from chamber 31onward through lines 29 and to control valves 32 and 53, respectively.

Due to the direct mechanical contact between the measuring plate 4 andlever 10 with the control slide 12, a constant ratio between the amountof air and fuel will be obtained as long as the characteristics of thesetwo control elements are sufficiently linear as desired. If this can beachieved, the air/fuel ratio in the mixture would be constant over thewhole working range of the engine. However, depending upon the actualworking conditions of the internal combustion engine, a richer or poorerair/fuel mixture will be required, and the variability required forresponding to these requirements is achieved according to the inventionby altering the resetting force of the measuring plate 4.

Measurable variables for load and speed of the internal combustionengine are the throttle valve position and pressure reduction in thesuction tube; therefore, the resetting force is varied most readily independence of these values. This is achieved by varying the force ofspring 37 in first pressure control valve 32 in accordance with theposition of throttle valve 7, and therefore with the pressure level inthe suction tube, by a corresponding rotation and/or axial displacementof cam 38. If, for instance, the throttle valve 7 is in a position underfull load, in which the suction tube is completely open, a maximalperformance is desired, Le. a relatively rich mixture is required. Toachieve this end, and since the tension of spring 37 in first pressurecontrol valve 32 determines the fuel pressure which is exerted on thefrontal face of control slide 12, the resetting force acting on themeasuring plate 4 must be decreased, so that the control slide 12 willbe moved to a position in which the control slots 24, 24' are openedmore widely and a correspondingly larger fuel amount can be injected. Inthe reverse case, under partial load operation, a relatively smallerdeflection of measuring plate 4 is obtained by a relatively higherpressure on the frontal face 13 of control slide 12.

When the engine runs under no load, cam 38 is displaced against spring44 due to a strongly reduced pressure in the suction tube, which resultsin a compression of spring 37 of the first pressure control valve 32.The compression of spring 37 increases the resetting force of measuringplate 4, so that in spite of the leakage of small amounts of air whichcan escape past the closed throttle valve 7, no deflection of measuringplate 4 and, therefore, no fuel injection takes place.

During the heating-up phase of the engine until the operationaltemperature is reached, the enrichment of the air/fuel mixture isdetermined by the control pressure influenced by pressure control valve53. In this case, control is effected in dependence on the ambienttemperature at the start. The closing force transmitted from membranespring 59 onto membrane 58 determines the control pressure in the supplysystem. At temperatures below the operational temperature, however,bimetallic spring 64 arrests the bearing 62 and rests against themembrane spring 59 thereby diminishing the force transmitted ontomembrane 58 via pin 60. Immediately after starting, however, bimetallicspring 64 is warmed up by electrical heater element 69, thus bendingspring 64 and reducing the arresting force exerted on membrane spring59. This force reduction is time-dependent and corresponds to the amountof heat transmitted onto bimetallic spring 64. In order for the decreaseof the force transmitted from bimetallic spring 64 onto membrane spring59 per unit of time to be as linear as possible and to correspond to theheating-up curves of the engine per unit of time, the electrical heaterelement 69 is not directly attached to bimetallic spring 64, but ismounted on the heat-conducting tongue 68, which can transmit its heat tothe bimetallic spring 64 by heat conduction via their joint mounting. Bybending heat conducting tongue 68 more or less strongly, the amount ofthermal radiation which is transmitted to the bimetallic spring 64 canbe varied. It is thereby possible to obtain a favorable adaptation ofthe tension-time behavior of the bimetallic spring 64 in the heating-upphase of the engine to the heating-up behavior of different engines. Thedesired basic tension is obtained by screwing bolt 65 more or lessdeeply into the housing 53a of pressure control valve 53, or by changingthe tension characteristic of membrane spring 59.

At starting temperatures below 0C, the heating-up of the engine per unitof time is represented by curves which are flatter the lower thetemperature.

.FIG. 2 shows these heating-up curves of the engine designated by d. Inorder to adapt these curves to starting temperatures of about 20C, theheating-up of bimetallic spring 64 must be retarded still further whichis achieved by means of the series resistance 74 in the current lead 72from electrical heating coil 69 to ground. At normal startingtemperatures, series resistance 74 is bridged by the second bimetallicspring 73, so that electrical heating coil 69 is heated up with the fullcurrent available. In FIG. 1 bimetallic spring 73 is shown in theposition switching in series resistance 74.

This above-described improved system affords a regulation of the controlpressure, and therewith also of the enrichment of the air/fuel mixture,which is adapted as far as possible to the actual operationalrequirements of the engine. This system takes into account theconsiderable differences in heating-up periods of an engine which occurat different starting temperatures.

What is claimed is:

1. In a fuel supply system for an externally ignited internal combustionengine with compression of the fuellair mixture, in which airflow-measuring means and a randomly operable throttle valve are arrangedsuccessively in the air intake suction pipe of the engine, and themeasuring means is moved, in proportion to the air amount flowingthrough the suction pipe, against an at least substantially constantresetting force and thereby displaces a movable member of a distributingvalve arranged in the fuel line in order to meter a fuel amountproportional to the air amount, and wherein a pressure liquid of atleast substantially constant pressure, which is continuously deliveredthrough a pressure line, serves to transmit the resetting force and actsupon a control slide valve to effect the resetting, the pressure of theliquid being variable by means of at least one regulated pressurecontrol valve which is controlled in dependence on characteristic enginedata, the improvement comprising, in combination, a control cell adaptedfor temperature-dependent operation and comprising a cell housing,bimetallic spring means, and heat-conducting tongue means jointlymounted in said housing for the conduction of heat from said tonguemeans to said bimetallic spring means and insulated against heat lossesto said housing, electrical heating means associated with said tonguemeans, and fuel pressure regulating means comprising a control springmounted in said housing, said bimetallic spring means being adapted forengaging said control spring and reducing the force of said spring attemperatures below the operational temperature of the engine.

2. The improvement as described in claim 1, wherein said tongue meanscomprise a metal strip arranged in parallel to said bimetallic springmeans and having heat-transfer contact therewith at said joint mountingin said housing, said electrical heating means being mounted on a freepart of said metallic strip.

3. The improvement as described in claim 2, wherein said control cellfurther comprises regulating means for regulating the heating up of saidelectrical heating means and thereby the degree of bending of saidbimetallic strip.

4. The improvement as described in claim 3, wherein said regulatingmeans comprise a second bimetallic spring means and a series resistancewhich can be switched-in by said second bimetallic spring means at lowstarting temperatures.

1. In a fuel supply system for an externally ignited internal combustionengine with compression of the fuel/air mixture, in which airflow-measuring means and a randomly operable throttle valve are arrangedsuccessively in the air intake suction pipe of the engine, and themeasuring means is moved, in proportion to the air amount flowingthrough the suction pipe, against an at least substantially constantresetting force and thereby displaces a movable member of a distributingvalve arranged in the fuel line in order to meter a fuel amountproportional to the air amount, and wherein a pressure liquid of atleast substantially constant pressure, which is continuously deliveredthrough a pressure line, serves to transmit the resetting force and actsupon a control slide valve to effect the resetting, the pressure of theliquid being variable by means of at least one regulated pressurecontrol valve which is controlled in dependence on characteristic enginedata, the improvement comprising, in combination, a control cell adaptedfor temperature-dependent operation and comprising a cell housing,bimetallic spring means, and heat-conducting tongue means jointlymounted in said housing for the conduction of heat from said tonguemeans to said bimetallic spring means and insulated against heat lossesto said housing, electrical heating means associated with said tonguemeans, and fuel pressure regulating means comprising a control springmounted in said housing, said bimetallic spring means being adapted forengaging said control spring and reducing the force of said spring attemperatures below the operational temperature of the engine.
 2. Theimprovement as described in claim 1, wherein said tongue means comprisea metal strip arranged in parallel to said bimetallic spring means andhaving heat-transfer contact therewith at said joint mounting in saidhousing, said electrical heating means being mounted on a free part ofsaid metallic strip.
 3. The improvement as described in claim 2, whereinsaid control cell further comprises regulating means for regulating theheating up of said electrical heating means and thereby the degree ofbending of said bimetallic strip.
 4. The improvement as described inclaim 3, wherein said regulating means comprise a second bimetallicspring means and a series resistance which can be switched-in by saidsecond bimetallic spring means at low starting temperatures.